So-called flash memories are known in the state of the art, particularly for use in digital telephone answering machines. A flash memory is a continuous, linear data storage. Known flash memories, e.g. from the INTEL Corporation (Santa Clara, Calif., have a 4 megabit (Mbit) memory divided into seven different size blocks. Memories from the Advanced Micro Devices (AMD) Company (Sunnyvale, Calif.) are divided into eight blocks. The flash memory from the INTEL Corporation can be combined into four blocks of equal size. In both of these known flash memories it is only possible to erase entire blocks. With a maximum storage time of 15 minutes e.g. and a subdivision into four blocks, this means that more then 3 minutes are stored in each block. To erase an entire block therefore, all messages that were recorded during these 3 minutes must be eliminated.
It is a disadvantage that all messages must be erased and that each new recording and erasing of a block also reduces the service life of the memory. Most flash memories have an average service life of 100,000 record-erase cycles per block.